One of the central processes regulating immune function involves T cells establishing cell-cell contacts with antigen-presenting cells (APCs) such as dendritic cells (DCs) via a contact zone known as the immunological synapse (IS). The importance of this synapse is considerable since interaction of T cells with DCs in lymph nodes is one of the critical steps in the generation of antigen specific immune responses which activate the nave T cells. Despite great technical advances in microscopic imaging, the development of techniques to dynamically monitor the cellular and the induced secretion patterns at the IS interaction on a single cell level to avoid ambiguities that arise due to heterogeneous responses in cell populations is lagging. It is the goal of the proposed work to develop a microfluidic droplt approach for dynamic monitoring of the biochemical events that transpire upon cell-cell communication in this key event of the immune response. In particular, the current proposal outlines the integration of a novel approach to monitor live cell surface expression changes as well as the actual immunological synapse (IS) formed between DCs and T cells. In addition to cell surface studies, the microfluidic droplet approach developed herein will also allow us to collect data on secreted molecules during IS formation utilizing microsphere sensors incorporated in the microfluidic reaction droplets. Thus, live cell secretion and cell surface changes will be monitored on a single cell level simultaneously in a distinct microenvironment, feat not possible using conventional techniques.